Glow-discharge microphone



May 3, 1927.

P. THOMAS GLOW mscnmez monoruoum Filed Jan. 25, 1924- INVENTOR WITNESSES:

- P/7////,03 Thomas I ATTORNEY Patented May 3, 1927. I I

EsPATsN-rjorriceg PHILLIPS THOMAS, or EDGEWOOD, PENNSYLVANIA, AssrGNoR 'ro (W STINGHOUSE I ELECTRIC a MANUFACTURING COMPANY,-A CORPORATION or PENNSYLVANIA.

GLOW-DISCHARGE, MIcnoriroNn.

, Application filed I January 25, 924. seria o. 688,379.

My invention relates to telephone systerns and apparatus and it has particular. relation to sound wave translating devices.

Broadly speaking, the object of my inven- 5 tion is to provide 7 an improvedtranslating device for convertingvibratorymotion 111 a fluid mediuminto vibratory-electric currents.

More specifically, an object of my inven-.

tion isto provide a telephonic transmitter 10 device whereby sound waves are more easily translated into correspondingly modulated electrical energy.

Another object of my invention is to Pro. vide a telephonic translating device which,

shall be characterized byits simplicity of design andopera'tion, and which lends itself to inexpensive production];

Another object of my nvention isto 'provide a telephonictranslating d-evicewhich shall be of greater sensitivity than: prior def vices.

' 'nother' object of my invention is to provide "a telephonic: translating device or the. glow-discharge type wherein theQihtensity of responseto pressure variations is substan tially independent; of the frequency of such variation. Q Q A further object of my invention is to produce a glow discharge transmitter" which I 30, is characterized by theuse of only two electrodesand by the use of a secondary cham her surrounding a portion of the glow discharge. j As disclosed in my copending application Serial No. 600,822, filed: November 14, 1922, glow discharge transmitten'a glow'discharge maintained between electrodes manifestsa varietyott characteristics by, which various portions can be recognized. These portions comprise a positive or anode column in contact with the positive electrode, and, following in sequence" toward the negative electrode, a Faraday darkspace, anegativelight, a cathode dark space and a cathode glow,

electrode. I have found that the voltage current characteristic of this glow discharge which latter is in contact with the negative of invention, I provide by the change "in current voltagecharacten pressure.

I have I have further found that" thissensitivity maybe greatly increased bysurrounding the positive electrode with a chamber. This f tl at the whole of the glow ldlschargevlsi'sensltlve fsound variations. 00,

chamber is also made to encloseithe posi- 'tive column of the, glow discharge and a small opening is provided for the passage of the current between, the electrodes.

transmitter constructed according to my in- VGIltlOll lS greater than that of; the ordinary carbon grain microphone and lt gives far more uniform response to various frequem sensitivity produced by my in- This construction produces: a glow discharge transmitter of high sensitivity and one of I uniform sensitivity to all vibrationfrequencies, -The sensitivity of the glowdischargeagency of a lesser number of sta-ges'of amplification than has heretofore been required. a

Other objects. and applications of my invention, asywell as structural details,wi1l

be apparent from the following description -when read in connection with'the accompanying drawing, wherein Fig. '1 'is'a diagrammatic view of a'pre- V ferred form of my lnvention incorporated into a sound-translating system,

F ig. g2 is a sectional view of the glow- The glowf discharge transmittercapsule- 1* comprises {a cylindrical '7 supporting portion discharge, transmitter capsule, taken along p corresponding to the line 11-11 in a i .95

4: having open 'ends a positive electrode I mounted :ina. screw 6, a negative'electrode 7 also mounted in a screw Sand a cuppiece 9, preferablvlofa nonconducting material and forming a chamber surrounding the positive electrode 5. The'fcup is of such size that all of its dimensions are less than j the-length of th-e' highest frequency sound y'wave to which it is intended to be responsive,

and that its dimensions are substantially greater than the average excursion of an air particle in the sounds of the mean magnitude to which it is to respond. The opeir ing of cup 9 is closed by a top plate 11, which may be of conducting material, containing a hole 12 for the passage of the current of the glow discharge.

Conductors 13 and 14 conduct current from mains 15 and 16 which, in turn, are connected to the current source 2.

The amplifier 8 may be coupled to the transmitter 1 by resistance, impedance, or transformer means. In Fig. 1 is shown a resistive coupling means and amplifier assembly which comprises a triode thermionic discharge device 21, a grid leak 22, a grid stopping condenser 23, an output transformer 24:, a plate current source 25, a filament current source 26 and a filament control rheostat 27. The negative terminal 7 of the glow discharge transmitter 1 is connected through a condenser 23 to the grid of a triode 21. The positive terminal 5 of the glow discharge transmitter 1 is connected by a lead 32 to the filament of the triode 21.

A grid leak 22 is shunted between the filament and the grid. The plate current source 25 and a transformer 24 are connected in series between the filament and the plate of triode 21 and the secondary of transformer 24 serves 'as an output means for the amplified current.

In the operation of my improved trans- -mitter, the sound waves to be translated into electrical variations enter either one or both of theopen ends of the cylindrical supporting portion 4. The sound waves, which, as is well known, comprise alternate zones of compression and rarefaction of the air, alter the voltage-current characteristics of the glow discharge.

It has not been possible as ,yet to determine the precise mode of ope 'ati'on of this modification of the glow discharge transmitter. From the information at present available, it is believed that the increase in sensitivity obtained by the addition of cup 9 and cover 11 is due to an air blast effect in and out through hole 12 in the cover 11 caused by pressure changes in the surrounding atmosphere.

It is probable that this air blast affects the positive column to accentuate-the voltage current characteristics. It is, however, found that the addition of this chamber, even though it is of relatively small volume, produces a very marked increase in the sen sitivity and response of the glow discharge to the vibratory influence of sound waves. Otherwise, the action of the transmitter is, in general, similar -to that described in my copending application previously mentioned.

In order to insure that the discharge will be a glow discharge and will continue to be a glow discharge, and not change into an arc,

I find that the source of potential must be high and that a current limiting device must be used. In addition to the specific di mensions already stated herein, the following actual constructions are noted. In one specific embodiment of my invention, I em-.

much smaller than in the glow discharge.

Another characteristic difierence is that with the glow discharge the electrodes are relatively cool, never becoming incandescent, while with an arc the electrodes are hot and the cathode is usually more incandescent than any portion of the arc itself.

Irrespective of the exact theory upon which my invention operates,-it is noted that variations in the voltage-current characteristics of the discharge may be amplifiedby" connecting a. suitable amplifying device across the terminals thereof. In the specific form illustrated, the voltage variations across the discharge cause corresponding changes acrOssthe resistor 22, which changes in turn cause the potential of the grid of the thermionic device to vary. The stopping condenser 23 serves to prevent the high ,potential from the source 2 from being applied to the grid of the triode 21.

In view of the foregoing, my invention provides means for producing a. marked increase in the sensitivity and response of a glow discharge transmitter as compared to one made according to previous systems of construction.

Vi/hile I have shown only one embodi- .ment of my invention in the accompanying drawings, it is capable of various changes and modifications without departing from the spirit and scope thereof, and it is desired, therefore, that only such limitations shall be 1mposed thereon as are indicated in the prior art or in the appended claims.

I claim as my invention:

1. In combination, a pair of spaced electrodes, respectively positive and negative exposed to atmospheric pressure, means for establishing a glow discharge therebetween,

and means for enclosing said positive electrode.

2. A translating device comprising a pair of spaced electrodes exposed to atmospheric pressure. means for establishing a glow discharge therebetween including a positive column, andfa member tive column.

v 3. A translatin device comprising a pair of spaced electro es exposed to atmospheric surrounding said posipressure, means forestablishing a glow discharge therebetween including a positive column, and a member surrounding said positive column, said member having a single opening therein. 7 p, I v

4. In an electrical system, the" combination with a pair of electrodes exposed to atmospheric pressure and constituting the positive and negative terminals of a discharge device, ofmeans for establishing a in pressure a tween said electrodes.

glow discharge therebetween including apositive column, and having at'voltage-current characteristic which varies with change in pressure, and meanscomprising a member surrounding said positive column for increasing said variation of said change in voltage-current characteristic with change 5. A glow discharge sound-responsive.de-

,vice comprising a pairof electrodes exposed to atmospheric pressure, a supporting means therefor, and means for enclosing one of said electrodes. I 1 V 6.-A glow discharge sound-responsive degvice comprising a'positive electrode and a negative electrode, supporting means for pcsitioning said respective electrodes, means for enclosing said positive electrode, and means for establishing a glow discharge be 7. A glow discharge sound-responsive device comprisinga positive electrode and a negative electrode, supporting means for positioning said respective electrodes, means "for enclosing said positive electrode, and

means for establishing a glow discharge betweensaid electrodes, said means comprising a source of direct; current having positive and negative terminals connected re- I spectively to saidelectrodes. .45

8. A sound translating system comprising a sound-responsive apparatus and an ampli- 'fying device, said sound-responsive apparatus comprisinga glow discharge transmitter having a positive electrode and a negative electrode, supporting means for positioning "said respective electrodes, a member' sur- ,rounding saidpositive electrode and means for. establishing a glow discharge between said electrodes.

9.-A sound translating system comprising a sound-responsive apparatus and an amplifying device, said sound-responsive apparatus I comprising a, glowd scharge transmitter having a positive electrode and a negative electrode, supporting means for positioning said respective Jelectrodes, a

member surrounding said positive electrode,

means for establishinga'glow discharge between said" electrodes, said amplifyingmea'ns electrode to said to saidpother electrode of said transmitter and an output means, and a source of current respectively connected between said cathode and said anode. v v '10. In a glow discharge sound-responsive device comprising apositive and a negative electrode, a sound .accentuating chamber surrounding said positive electrode.

11. In a glowdischargesound-responsive device'comprisinga positive and a negative electrode, andmeans for producing a glow discharge therebetween, a chamber surrounding said positive'electrode,the dimensions of said chamber being less than the length of the shortest sound wave to which it is intended to Y respond, and greater than the average excursion of a particle ofair produced by successive soundwaves. c

12. In a glow discharge sound-responsive device comprising a positive electrode, a

negative electrode, and meansvfor producing a glow discharge therebetween having a' positive column, and'means for intensifying the response ofsaid positive column to sound, said means comprising a chamber surrounding said positive electrode.

'13. ,A glow discharge sound-responsive device comprising apositiveelectrode and a I negative electrode, means for producing a glow discharge therebetween, comprising a porting means of insulating'material for said electrodes fortso spacing them as to cause thefpassage of said glow discharge, a chamber surrounding said positive electrode,

positive column and said source'of high voltage direct current, sup

said'chamber comprising a non-conducting cup having a bottom that is drilled and tapped for the passage of said positive elec-' tro'de, and a metallic cover closing the top opening of said cup, said cover being drilled forthe passageof said glowdiscliarge.

14. A translating device comprising a pair of spaced electrodes, means for establishing a glow discharge therebetween, including a positive column, and a chamber surrounding said positive column, said chamber having a single opening thereto that is adapted and positioned for the passage of the glow discharge 'therethrough.

Iii-testimony whereof, I have hereunto subscribed my name this 17th day of Jan nary, 192 i. f I

PrnLLiPs THOMAS. 

